JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
          <div id="circle">
          </div>
        </div>

CSS

#container {
       height:50%; width: 50%;
       padding:1%;
      position:absolute;
    }
    #circle {
       background-color:blue;
       border-radius:50%;
       height:96%; width:96%;
       position:absolute;
    }

JavaScript

$(window).resize(function() {
$('#container').width($('#container').height());
});